This invention pertains to a demodulator applicable to the demodulation of polyphase voltages of n phases interfering among themselves by constituting a system of polyphase pseudo-sinusoidal voltages modulated in amplitude to a pulsation .epsilon., in order to obtain a system of polyphase voltages of pulsation .epsilon..
The interference between two sinusoidal voltages of frequencies f.sub.1, f.sub.2 or pulsations .omega..sub.1, .omega..sub.2, and of different amplitudes U.sub.1, U.sub.2 is a well known phenonmenon, currently used in radio, in the technique of synchroscopes, of transmitters, etc.
This phenomenon may be summarized by the following equation: EQU U(t)=U.sub.1 sin .omega..sub.1 t+U.sub.2 sin .omega..sub.2 t=2U.sub.o cos (.epsilon.t) sin (.omega.t)+2e sin (.epsilon.t) cos (.omega.t) (1)
in which EQU .omega..sub.1 =.omega.+.epsilon. EQU .omega..sub.2 =.omega.-.epsilon.
and EQU U.sub.1 =U.sub.o +E EQU U.sub.2 =U.sub.o -e
where .omega.=average pulsation and U.sub.o =average voltage of the component sinusoidal voltages.
The general nature of this voltage, resulting from the "pulsating" U(t), is given in FIG. 1 by the solid line C.sub.1.
Of course, if two systems of polyphase voltages are placed in series, phase to phase, n voltages analogous to the preceding, within the same envelope, but differing in phase by 2.pi./n (n being the number of phases for each system) are obtained. FIG. 2 shows the graphs of these voltages which, mathematically, may be expressed as follows: EQU U.sub.A =U.sub.1 sin (.omega..sub.1 t)+U.sub.2 sin (.omega..sub.2 t) (graph 1) ##EQU1##
In addition, if the differential voltage e=0, that is if U.sub.1 =U.sub.2 =U.sub.o the resulting voltage U(t)=2U.sub.o cos .epsilon.t sin .omega.t, may be described as a "pseudo-sinusoidal" voltage of pulsation .omega., and variable amplitude 2U.sub.o cos .epsilon.t. The same is true for the resulting voltages from the 2 polyphase systems placed in series, phase to phase, and previously described. This corresponds to the case of FIG. 3a in which: EQU U.sub.a.sbsb.1 =U.sub.o sin (.omega..sub.1 t)+U.sub.o sin (.omega..sub.2 t)=U.sub.11 +U.sub.21 (graph a.sub.1) ##EQU2## In addition, if we proceed to circular permutations of the phases of the second polyphase system in relation to the first, we obtain n groups of voltages, the general aspect of which is similar to that of the first group, but the respective envelopes of which are staggered between themselves. Thus we see on FIGS. 3a, 3b, and 3c the example of three groups of voltages with: ##EQU3## The vectorial representation of these equations appears on FIGS. 4a, 4b, and 4c, in which the system U.sub.11, U.sub.12, and U.sub.13 rotates at a speed (.omega.t+.epsilon.t) and the system U.sub.21, U.sub.22, and U.sub.23 rotates at the speed (.omega.t-.epsilon.t). The resulting voltages (U.sub.a.sbsb.1, U.sub.a.sbsb.2, U.sub.a.sbsb.3), (U.sub.b.sbsb.1, U.sub.b.sbsb.2, U.sub.b.sbsb.3), and (U.sub.c.sbsb.1, U.sub.c.sbsb.2, U.sub.c.sbsb.3) form three "pseudo-triphase" systems of variable amplitudes respectively equal to U.sub.A.sbsb.o =2U.sub.o cos .epsilon.t, U.sub.B.sbsb.o =2U.sub.o ##EQU4##
An object of this invention is to provide a novel system for the utilization of this "pulsating" phenomenon to obtain a system of polyphase voltages with a given, constant or variable frequency f, and corrresponding to the pulsation .epsilon. from an electric generator producing voltages responding to the above described equations (3, 4, and 5).
A more specific object of this invention is to provide a novel demodulator which responds to systems of polyphase voltages with n phases and responding to n systems of n equations of the kinds of (3) to (5), to provide a system of n polyphase voltages presenting a frequency corresponding to the pulsation .epsilon. of the modulation in amplitude of the component voltages of the said systems of polyphase voltages.
Known modulators of this general kind use the various rectifier electronic components. However, such modulators are rather involved and require the use of a large number of such components, which increases the cost and decreases the reliability of the system.
This invention aims specifically at coping with the aforementioned disadvantages and at permitting signal demodulation of the kind previously mentioned in a manner altogether simple, effective, and reliable. These goals are attained through a demodulator according to the invention which comprises a polyphase rotating machine including basically (a) n armatures at n phases interconnected by means of a common yoke made up of a low loss magnetic material and fed by n systems of polyphase pseudo-sinusoidal voltages modulated in amplitude at a pulsation .epsilon., (b) a freely rotatable rotor, comprising n magnetic circuits interconnected through a common magnetic axle having its flux carrying parts of a low loss magnetic material, and (c) n static coils concentric with the axis of the magnetic axle and at the terminals of which n systems of polyphase voltages of pulsation .epsilon. are collected, which rotating machine is such that each of the n magnetic circuits of the rotor bears a number of polar masses equal to the number of pairs of poles on the corresponding armature, and the relative geometric keyings of homologous phases of the n armatures of the stator are identical to the relative longitudinal keyings of the polar masses of the rotor.
The demodulator, according to the invention, permits the realization of machines the size and weight of which are relatively small compared to the amounts of energy collected, and to the speeds of rotation which may be very high.
According to one embodiment of the invention, the parts of the rotor and of the yoke subjected to an alternating magnetic flux are made up of stacked laminated sheet steel including first stacks of sheet steel which are parallel to the axis of the rotor and surrounded and bound by second stacks of sheet steel which are perpendicular to the axis of the rotor.
According to one particular embodiment of the invention, the first stacks of sheet steel, parallel to the axis of the rotor are made up of stacks of flat sheet steel incorporated into the polar masses of the rotor.
According to another embodiment of the invention, the first stacks of sheet steel, parallel to the aixs of the rotor form a crown concentric with the axis of the rotor and made up of a complex of sheet steel forming portions of a cylinder in the form of an involute of a circle.
According to still another embodiment of the invention, the first stacks of sheet steel, parallel to the axis of the rotor, are mounted on the rotor in the fashion of insulating plates of the collector of a direct current machine.
Other characteristics, objects and advantages of the invention will be better understood from reading the following detailed description of the specific forms of the invention, given only as non-limitating examples, with reference to the attached drawings.